1. Field of the Invention
The present invention relates to a sound absorbing device for a supersonic jet propelled engine.
2. Description of the Related Art
FIG. 7 shows a longitudinal sectional view showing a turbo fan engine which is a typical example of a supersonic jet propelling engine. The propelling engine is composed of, from a front side, a fan 101, a compressor 102, a burner 103, a high pressure turbine 104, a low pressure turbine 105, an after-burner 106 and an exhaust gas nozzle 107. A combustion gas 6 generated in a gas generator portion (indicated by the reference numerals 101 to 106) flows in a direction indicated by the arrow to be injected through the exhaust gas nozzle 107 into the atmosphere.
FIG. 8 is an enlarged longitudinal sectional view showing the exhaust gas nozzle 107 shown in FIG. 7. In FIG. 8, there are shown a liner 1, a nozzle plate 5, an outer plate 15 of the exhaust gas nozzle 107, the high temperature combustion gas 6 that flows at a high speed through the nozzle and cooling air 7 that flows between the liner 1 and the nozzle plate 5 for preventing elevation of the temperature of the liner 1. As is apparent from the drawings, the conventional super sonic jet propelling engine is not provided with any sound absorbing material that is usable with the high temperature combustion gas which would be kept at a temperature of about 2,000.degree. C. Therefore, it is impossible to effect the sound absorbing function for preventing the sound or noise generation associated with the flow of exhaust gas.
In a conventional subsonic airplane jet propelling engine, a fan gas is mixed with the exhaust gas by a flow mixer to decrease the temperature of the exhaust gas, and noise is reduced by applying a sound or noise absorbing material to the mixer. However, it is impossible to adopt such a noise reduction technique since it is impossible to increase a bypass ratio from the fan in the subsonic airplane engine.
An object of the present invention is to provide a sound absorbing apparatus for a supersonic airplane engine, which may work at a high temperature.